US3842905A

US3842905A - Oil well cementing plug

Info

Publication number: US3842905A
Application number: US00136928A
Authority: US
Inventors: O Morrisett; G Boehm
Original assignee: Halliburton Co
Current assignee: Halliburton Co
Priority date: 1971-04-23
Filing date: 1971-04-23
Publication date: 1974-10-22
Anticipated expiration: 1991-10-22

Abstract

This invention relates to an oil well cementing plug having a fluid relief passageway therethrough, such passageway containing a rod which maintains a fluid tight seal across said passageway until the rod is removed therefrom.

Description

[451 Oct. 22, 1974 Morrisett et al.

166/155 166/154 Baker et a1. 166/154 2,560,901 7/1951 2,655,216 10/1953 Baker et a1. 2,662,600 12/1953 Primary Examiner.1ames A. Leppink Okla.

Attorney, Agent, or Firm-John H. Tregoning [22] Filed: Apr. 23, 1971 Appl. No.: 136,928

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moved therefrom.

[56] References Cited UNlTED STATES PATENTS 12/1935 C0nnolly...............

p rgmmnmzzmm SHEET 10F 3 I NVENTORS O. L. Morrisefr Gail M. Boehm ATTORN Z \N \U T I. mt Q i w I M fi aQ N I i I m \N\\\\\ INVENTORS Gui! oehm QZ/ FIGURE 2. FIGURE 20. FIGURE 2b.

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ATTORNEY PATENTEDBCIZZIHM SIEET 3 [if 3 FIGURE illiliilrtlll M 1 41 1 11!!! INVENTORS O. L. Morriserr Gail M. Boehm ATTORN 1 on. WELL-CEMENTING PLUG BACKGROUND OF THE INVENTION It is common practice in cementing long strings of casing to use a multiple stage cementing tool which contains two sliding sleeves, one above the other. The lowest sleeve is moved by dropping a plug from the surface onto a seat in the sleeve. A fluid tight seal is established at that point. Pump pressure acting across the plug pushes both the plug and sleeve downwardly a short distance. When the upper sleeve is to be moved, a second plug is dropped from the surface onto a seat in the upper sleeve; as in the lower sleeve, a fluid tight seal is effected thereon. Pump pressure pushes the second plug and the upper sleeve downwardly.

As might be expected, as the second plug and upper sleeve start to move downwardly, fluid trapped between the two plugs becomes compressed and exerts an upward force against the second plug. This force often builds up to where it equals the pump pressure, making further downward movement difficult.

The present invention provides an oil well cementing plug which comprises an elongated housing having a fluid relief passageway therethrough, a rod slidably positioned in the passageway and retaining means for temporarily holding the rod in the passageway.

THE DRAWINGS An oil well cementing plug constructed in accordance with the invention is illustrated in the accompa- DETAILED DESCRIPTION Referring to FIG. 1, shown therein and generally designated by the reference character 11 is a cementing plug constructed in accordance-with the invention. The plug 11 includes a. generally U-shapedouter shell 12 which is constructed from an easily drillable material such as aluminum or cast iron. The desirability of using such material will be explained later. Upper end 13 of shell 12 contains a plurality of fins 14 to give stability to the plug when dropped into a well bore (not shown). Directly below fins 14, shell 12 forms an annular outwardly projecting ring 15 which provides a downwardly and inwardly tapered surface 16. As will be shown later, surface 16 mates with a corresponding surface in a multiple stage cementing tool.

Lower end 18 of shell 12 contains passageway 19.

A number of recesses 20 are provided on inner wall 21 of shell 12. These recesses 20 provide an anchor for filler 22 which is packed into shell 12 asshown in FIG. 1. Filler 22 can be composed of any number of drillable substances such as cement, rubber, or plastic. Preferrably, a plastic mixed with iron powder is used; this mixture adds weight to plug 11 without being difficult to drill.

A sleeve 24 extends axially through the center of plug 11. Its lower end 25 is positioned in aforementioned passageway 19 of shell 12 and is attached thereto via companion threads 26. Its upper end 27 terminates within the body of filler 22 but just below upper end 13 of shell 12.

A rod retainer 30 is attached to upper end 27 of sleeve 24 via companion threads 31. Retainer 30 extends from sleeve 24 upwardly above upper end 13 of shell 12. The upper portion of retainer 30 extending above plug 11, designated at 32, contains two or more shear pins 34.

Sleeve 24 andretainer 30 cooperate to form a passageway, designated at 35, extending from upper end 32 of retainer 30 downwardly through retainer 30 and sleeve 24, emerging on the surface of shell 12 at lower end 18.

An elongated rod 40 occupies passageway 35 as shown in FIG. 1. Previously mentioned shear pins 34 extend into apertures 42 on rod 40, holding the rod in the position shown. An O-ring 43, partly recessed in the section of passageway 35 located in retainer 30, provides a fluid tight seal between retainer 30 and rod 40. The need for this sea] will be shown below. The lower end of rod 40, designated at 44, is threaded to receive a nut 45. The body of nut 45 extends outwardly perpendicularly to the axis of rod 40, and contacts lower end 18 of shell 12. This arrangement prevents upward movement of rod 40 and the accidental shearing of pins 34 by some force which could strike lower end 44 of rod 40.

Rod 40 has three sectionsdesignated by the letters A, B, and C. Section A includeslowerend 44 and the threaded portion adapted to receive nut 45. Section B, extending upwardly through plug 11 and terminating immediately above upper end 32 of retainer 30, has a diameter slightly less than that of passageway 35 through which rod 40 passes. Section C is characterized by having a smaller diameter than has section B. The reason for this is so that rod 40 need move downwardly only a short distance to remove the sealing effectof O-ring 43.

OPERATIONOF THE EMBODIMENT OF FIG. 1

FIGS. 2, 2a, and 2b illustrate the operation of the instant invention. In FIG. 2, casing 60, which is being cemented into well 61, contains multiple stage cementing tool 62, shown schematically, which includes lower sleeve 63, covering ports 64, and upper sleeve 65. Sleeve 63 includes an inwardly tapered surface 63a. Cementing plug 11, containing rod 40, has been dropped from the surface of the well and is free falling downwardly through casing 60. A preceding stage of cement slurry 66 has already been pumped down casing 60, out thereof and back up the annular space 67 to a point near tool 62.

FIG. 2a shows that plug 11 has landed in lower sleeve 63, surface 16 lodging on surface 63a. Both sleeve 63 and plug 11 have been pumped down to rest on shoulder 68 in tool 62. Ports 64 have been opened by this event and another stage of cement slurry 69 is being pumped down casing 60, through the ports and out into annular space 67. Slurry 69 cannot move downwardly through tool 62 because rod 40 and aforementioned O-ring 43 prevents flow through passageway 35 in plug 11, and also, a fluid tight seal is established between surface 16 of plug 11 and surface 63a of lower sleeve 63. A closing plug 70, following cement slurry 69, will land on upper sleeve 65 so that sleeve 65 can be moved down closing ports 64, thus completing the cementing operation.

FIG. 2b illustrates the operational feature of the instant invention. Closing plug 70 has landed in upper sleeve 65 which now moves down across ports 64; cement slurry 69 remaining within tool 62 is trapped and would begin to be compressed, except, before that can happen, closing plug 70 strikes rod 40 causing the shearing of pins 34 (FIG. 1) in plug 11. Rod 40, no longer retained, drops from plug 11 leaving passageway 35 therein unobstructed so that cement slurry 69, otherwise trapped, can escape therethrough. Upper sleeve 65 can now completely close without difficulty.

DESCRIPTION OF THE EMBODIMENT OF FIG. 3

FIG. 3 illustrates a second embodiment of the instant invention. Plug 111 consists of a housing 112 having upper end 113 and lower end 114. Housing 112 is made from drillable material such as aluminum or cast iron. An axial passageway 115 extends completely through housing 112 and consists of three sections designated by the letters D, E, and F. Section D, extending upwardly from lower end 114, is the lowest section. Section E, the middle section, has a smaller diameter than does section D. Housing 112 contains two or more shear pins 116 which extend into section E of passageway 115. Section F is the upper section and has a smaller diameter than does section E.

A U-shaped cap 117, having a plurality of holes collectively numbered 118, is attached to lower end 114 of housing 112 via companion threads 119. Positioned on housing 112 immediately above cap 117, is an annular resilient centralizer blade 120 and two annular

cupshaped wiper blades

121 and 122. Spaced above blade 122 and separated therefrom by a spacer sleeve 123, is an annular outwardly projecting ring 124 having a downwardly and inwardly tapered surface 125 which mates with surface 63a (FIG. 2). Ring 124 is attached to housing 112 via companion threads 126.

A nut 127, having an outwardly projecting flange 128 is attached to housing 112 above ring 124 via companion threads 129. A second annular cantralizer blade 130 is positioned on nut 127 between ring 124 and flange 128.

A rod, designated at 131 is initially partly positioned in passageway 115 as shown in FIG. 3. Rod 131 consists of a short lower section 132 and an elongated upper section 133. Lower section 132, containing an O-ring 134 and two apertures 135, has a diameter which substantially complements that of section E of passageway 115. Aforementioned shear pins 116 extend into apertures 135, holding rod 131 in the position shown. ring 134 provides a fluid tight seal between rod 131 and the walls 136 of section E so that fluid cannot pass through passageway 115 as long as rod 131 is retained by shear pins 116.

The diameter of the elongated upper section 133 of rod 131 is less than that of lower section 132 and may substantially complement that of secion F of passageway 115. The tolerance between section F and upper section 133, however is not so close as to restrict movement of section 133 therethrough.

OPERATION OF THE EMBODIMENT OF FIG. 3

In that the operation of cementing plug 111 is akin to that of plug 11 (FIG. 1) described in detail above,

minor one, is that plug 111, when placed into well 61, must be pumped down casing 60 and into tool 62. This is so because

blades

121 and 122, whose diameters exceed that of the internal diameter of casing 60, wipe the casing walls clean of residue cement and/or drilling mud (not shown) and push such matter ahead thereof.

The second feature relates to rod 131 in plug 111. As will be recalled, a cap 117 is attached to the lower end of plug 111. This cap confines rod 131 within passageway after closing plug 67 (FIG. 2b) has struck the rod and sheared pins 116. As is apparent from FIG. 4, after rod 131 has dropped down to where it is resting on cap 117 and is mostly in section D of passageway 115, cement slurry 69, trapped in tool 62, will be able to flow downwardly through the passageway, around rod 131, and out holes 118 in cap 117. Retaining the rod within plug 111 is simply for convenience in that it will be drilled up at the same time as the rest of the plug. In fact, plug 111 can be constructed so that cap 117 has a single center bore 118 large enough to permit rod 131 to drop out of plug 111.

From time to time in the above descriptions, references have been made to the materials used in constructing the present invention. Although the cementing plugs can be structured so as to be retrievable from the surface, it is much more desirable to simply drill them up into small pieces and flush the pieces out of the well. For this reason, the material preferrably used for the rigid parts is aluminum, a material exceptionally susceptible to the drill bit. Any number of rubbers, natural or man-made, can be used for the resilient parts as they too can be drilled up easily; care being taken here in regart to chemical reactions possible between such rubber and the slurry and/or other fluids the rubber may contact.

The present invention has been described in a multiple stage cementing operation. However, its use is not to be considered so limited. As the utility of the invention becomes better known and appreciated, more and different uses will become apparent.

It will be apparent that many different embodiments of this invention, other than those described herein, may be made without departing from the spirit and scope thereof. Therefore, the instant invention is not intended to be limited except as indicated in the appended claims.

What is claimed is:

1. An oil well cementing plug, which comprises:

a. an elongated housing having a fluid pressure relief passageway therethrough;

b. a rod slidably and sealingly positioned in said passageway;

c. frangible retaining means between said rod and said housing and arranged to maintain said rod in a sealing relationship with said housing until said frangible retaining means are sheared; and

d. said rod adapted to move out of sealing contact with said housing upon shearing of said frangible retaining means.

2. The cementing plug of claim 1 wherein said housing includes an outer shell and an inner filler.

3. The cementing plug of claim 2 wherein:

a. said outer shell is made from aluminum; and

b. said inner filler is made from epoxy resin and powdered lead.

4. The cementing plug of claim 3 wherein said inner filler is made from epoxy plastic and ferrophosphorus.

5. A plug used in oil and gas well cementing operations, which comprises:

a. a hollow case having a plurality of fins at one end thereof;

b. a liner attached to and extending longitudinally through said case, said liner defining a fluid passageway;

c. a filler positioned in said case, said flller filling the space between said case and said liner;

d. a rod slidably positioned in said fluid passageway, said rod having at least one aperture positioned thereon; and

e. means for temporarily retaining said rod in said passageway.

6. The plug of claim 5 wherein said case is made from aluminum.

7. The plug of claim 5 wherein said case is made from cast iron.

8. The plug of claim 5 wherein said filler is made from plastic.

9. The plug of claim 5 wherein said means for retaining said rod includes a member attached to one end of said liner, said member having a bore extending axially therethrough and concentric with said passageway in said liner, said bore adapted to receive said rod, and at least one shear pin extending laterally into said bore, said at least one shear pin adapted to mate with said at least one aperture in said rod.

10. A plug for use in oil well cementing operations, which comprises:

a. an elongated body having a passageway extending axially therethrough;

b. A U-shaped cap attached to the lower end of said body, said cap having one or more bores extending therethrough;

c. a rod slidably and sealingly positioned in said passageway; and

d. frangible means for temporarily retaining said rod in said passageway.

11. The plug of claim wherein:

a. said body contains a plurality of resilient wiper blades disposed about said body; and

b. said rod contains seal means thereon whereby said seal means in cooperation with the walls of said passageway provide a fluid tight seal in said passageway.

12. The plug of claim 10 wherein one of said bores on said U-shaped cap is adapted to pass said rod therethrough.

13. A plug for use in oil well drilling, cementing and testing tools where said tools contain inwardly projecting seats, said plug comprising:

a. an elongated housing having an annular projection thereon, said projection adapted to engage the inwardly projecting seats in the drilling, cementing and testing tools; said housing including an outer shell and an'inner filler, said filler filling the space between said shell and said liner;

b. a liner defining a passageway, said liner attached to and extending axially through said housing;

c; a rod slidably positioned in said passageway, said rod having at least one aperture thereon; and,

d. means for temporarily retaining said rod in said passageway.

14. The plug of claim 13 wherein said outer shell is made from aluminum and said filler is made from epoxy plastic and powdered lead.

15. The plug of claim 13 wherein said means for temporarily retaining said rod in said passageway includes a member attached to one end of said liner, said member having a bore extending axially therethrough adapted to receive said rod.

16. The plug of claim 15 wherein said member contains at least one shear pin extending laterally into said bore, said at least one shear pin adapted to mate with at least one aperture in said rod.

17. The plug of claim 16 wherein said member contains sealing means in said bore whereby said sealing means, in cooperation with said rod, provides a fluid tight seal in said bore.

18. Plug apparatus for sealing off the internal bore of oil well casing and tubing and, when used with other plug apparatus, capable of preventing an hydraulic lock therebetween, comprising:

a. elongated external housing means containing a longitudinal axial bore therein;

b. an elongated fluid pressure relief means slidably and sealingly located within said axial bore in said housing and frangibly attached to said housing;

c. said pressure relief means extending out of said bore above said housing and adapted to be contacted from above by actuating plug means whereby said pressure relief means is moved out of sealing engagement with said housing;

d. frangible shear means temporarily connecting said pressure relief means to said housing means; and

e. first seal means located externally on said housing in annular arrangement adapted to sealingly engage the internal bore of the wall casing or tubing.

19. The plug apparatus of claim 18 wherein said axial bore extends completely through said housing means and said pressure relief means comprises an elongated rod located in said axial bore and extending completely therethrough, said rod containing second seal means thereon, and said axial bore in said housing means having an enlarged lower section adapted to allow said second seal means to pass unrestricted downward therethrough.

20. The plug apparatus of claim 19 wherein said elongated rod also extends out of the bottom of said bore in said housing means and said plug apparatus further comprises upward travel preventing means fixedly attached to the lower protruding end of said elongated rod; said preventing means adapted to abut the lower end of said housing means thereby preventing upward movement of said rod in said housing means and premature shearing of said frangible means.

21. The plug apparatus of claim 20 wherein said housing means further comprises an inner annular seal ing surface located within said axial bore above said enlarged lower section of said axial bore in said housing means; said inner annular sealing surface adapted to sealingly engage said second seal means on said elongated rod. 1

22. The plug apparatus of claim 21 wherein said first seal means comprises an outwardly extending exterior annular shoulder attached to said housing means, said shoulder adapted to seat and sealingly engage in an internal annular seat in the well casing or tubing.

inner annular sealing surface above said enlarged lower section adapted to sealingly engage said second seal means on said elongated rod.

24. The plug apparatus of claim 23 further comprising retaining means fixedly attached to said housing means and located at the bottom thereof, said retaining means having one or more fluid passages therethrough communicating with said bore passage; said retaining means arranged to prevent said rod from sliding completely downward out of said enlarged portion of said axial bore.

25. The plug apparatus of claim 24 wherein said first seal means comprises one or more outwardly extending elastomeric wiper elements adapted to sealingly engage the internal bore of said tubing or casing.

26. The plug apparatus of claim 25 further comprising one or more annular centralizing blades attached to said housing means, and outwardly extending exterior annular valve seating means; said seating means further comprising an annular ring having a downwardly and inwardly tapered seating surface located circumferentially thereon.

Claims

1. An oil well cementing plug, which comprises: a. an elongated housing having a fluid pressure relief passageway therethrough; b. a rod slidably and sealingly positioned in said passageway; c. frangible retaining means between said rod and said housing and arranged to maintain said rod in a sealing relationship with said housing until said frangible retaining means are sheared; and d. said rod adapted to move out of sealing contact with said housing upon shearing of said frangible retaining means.

3. The cementing plug of claim 2 wherein: a. said outer shell is made from aluminum; and b. said inner filler is made from epoxy resin and powdered lead.

5. A plug used in oil and gas well cementing operations, which comprises: a. a hollow case having a plurality of fins at one end thereof; b. a liner attached to and extending longitudinally through said case, said liner defining a fluid passageway; c. a filler positioned in said case, said filler filling the space between said case and said liner; d. a rod slidably positioned in said fluid passageway, said rod having at least one aperture positioned thereon; and e. means for temporarily retaining said rod in said passageway.

6. The plug of claim 5 wherein said case is made from aluminum.

7. The plug of claim 5 wherein said case is made from cast iron.

8. The plug of claim 5 wherein said filler is made from plastic.

10. A plug for use in oil well cementing operations, which comprises: a. an elongated body having a passageway extending axially therethrough; b. A U-shaped cap attached to the lower end of said body, said cap having one or more bores extending therethrough; c. a rod slidably and sealingly positioned in said passageway; and d. frangible means for temporarily retaining said rod in said passageway.

11. The plug of claim 10 wherein: a. said body contains a plurality of resilient wiper blades disposed about said body; and b. said rod contains seal means thereon whereby said seal means in cooperation with the walls of said passageway provide a fluid tight seal in said passageway.

13. A plug for use in oil well drilling, cementing and testing tools where said tools contain inwardly projecting seats, said plug comprising: a. an elongated housing having an annular projection thereon, said projection adapted to engage the inwardly projecting seats in the drilling, cementing and testing tools; said housing including an outer shell and an inner filler, said filler filling the space between said shell and said liner; b. a liner defining a passageway, said liner attached to and extending axially through said housing; c. a rod slidably positioned in said passageway, said rod having at least one aperture thereon; and, d. means for temporarily retaining said rod in said passageway.

18. Plug apparatus for sealing off the internal bore of oil well casing and tubing and, when used with other plug apparatus, capable of preventing an hydraulic lock therebetween, comprising: a. elongated external housing means containing a longitudinal axial bore therein; b. an elongated fluid pressure relief means slidably and sealingly located within said axial bore in said housing and frangibly attached to said housing; c. said pressure relief means extending out of said bore above said housing and adapted to be contacted from above by actuating plug means whereby said pressure relief means is moved out of sealing engagement with said housing; d. frangible shear means temporarily connecting said pressure relief means to said housing means; and e. first seal means located externally on said housing in annular arrangement adapted to sealingly engage the internal bore of the wall casing or tubing.

21. The plug apparatus of claim 20 wherein said housing means further comprises an inner annular sealing surface located within said axial bore above said enlarged lower section of said axial bore in said housing means; said inner annular sealing surface adapted to sealingly engage said second seal means on said elongated rod.

23. The plug apparatus of claim 18 wherein said axial bore extends completely through said housing means and said pressure relief means comprises an elongated rod located partially within said axial bore and extending above said housing means; said rod containing second seal means around the lower end thereof; and said axial bore in said housing means having an enlarged lower section adapted to allow said second seal means to pass unrestricted downward therethrough and an inner annular sealing surface above said enlarged lower section adapted to sealingly engage said second seal means on said elongated rod.